Context. The object HD 43587Aa is a G0V star observed during the 145-day LRa03 run of the COnvection, ROtation and planetary Transits space mission (CoRoT), for which complementary High Accuracy Radial ... [more ▼]

Context. The object HD 43587Aa is a G0V star observed during the 145-day LRa03 run of the COnvection, ROtation and planetary Transits space mission (CoRoT), for which complementary High Accuracy Radial velocity Planet Searcher (HARPS) spectra with S/N > 300 were also obtained. Its visual magnitude is 5.71, and its effective temperature is close to 5950 K. It has a known companion in a highly eccentric orbit and is also coupled with two more distant companions. <BR /> Aims: We undertake a preliminary investigation of the internal structure of HD 43587Aa. <BR /> Methods: We carried out a seismic analysis of the star, using maximum likelihood estimators and Markov chain Monte Carlo methods. <BR /> Results: We established the first table of the eigenmode frequencies, widths, and heights for HD 43587Aa. The star appears to have a mass and a radius slightly larger than the Sun, and is slightly older (5.6 Gyr). Two scenarios are suggested for the geometry of the star: either its inclination angle is very low, or the rotation velocity of the star is very low. <BR /> Conclusions: A more detailed study of the rotation and of the magnetic and chromospheric activity for this star is needed, and will be the subject of a further study. New high resolution spectrometric observations should be performed for at least several months in duration. [less ▲]

Rotation is expected to have an important influence on the structure and the evolution of stars. However, the mechanisms of angular momentum transport in stars remain theoretically uncertain and very ... [more ▼]

Rotation is expected to have an important influence on the structure and the evolution of stars. However, the mechanisms of angular momentum transport in stars remain theoretically uncertain and very complex to take into account in stellar models. To achieve a better understanding of these processes, we desperately need observational constraints on the internal rotation of stars, which until very recently was restricted to the Sun. In this paper, we report the detection of mixed modes—i.e., modes that behave both as g modes in the core and as p modes in the envelope—in the spectrum of the early red giant KIC 7341231, which was observed during one year with the Kepler spacecraft. By performing an analysis of the oscillation spectrum of the star, we show that its non-radial modes are clearly split by stellar rotation and we are able to determine precisely the rotational splittings of 18 modes. We then find a stellar model that reproduces very well the observed atmospheric and seismic properties of the star. We use this model to perform inversions of the internal rotation profile of the star, which enables us to show that the core of the star is rotating at least five times faster than the envelope. This will shed new light on the processes of transport of angular momentum in stars. In particular, this result can be used to place constraints on the angular momentum coupling between the core and the envelope of early red giants, which could help us discriminate between the theories that have been proposed over the last few decades. [less ▲]